Temperature controllers that are equipped with PID controlling functions are used in order to control temperatures in heat treatment furnaces, and the like. In a temperature regulator, it is necessary to set a large number of parameters, such as PID parameters. The temperature regulator performs PID calculations using the PID parameters, to output a manipulated variable MV that will cause the measured temperature PV to go to the set point SP that is set to the target temperature. This makes it possible to cause the measured temperature PV (the process variable PV) to approach the target temperature (the set point SP). Consequently, setting of the PID parameters, and the like, is necessary and important.
However, the control result information (data for characteristic values in control response, such as the time to arrival at the set point, the amount of overshoot, and so forth) is useful information, as the result of control for the actual control target, when ascertaining states wherein there are problems in control, and when adjusting the PID parameters. Because of this, a function is executed wherein characteristic values for the control response within the temperature controller are calculated, and are stored within the temperature controller, as the series of control operations, such as heating and cooling, are performed. See, for example, Japanese Unexamined Patent Application Publication No. 2009-217439 (the “JP '439”). On the other hand, there are also devices, such as data loggers, that collect and record all measured data. See, for example, Japanese Unexamined Patent Application Publication No. 2008-286603 (the “JP '603”). The data collecting functions disclosed in the JP '439 and the JP '603 enable the characteristic values for the control response in PID control, or all time series data, to be collected, to be subject to monitoring, and to be processed as subject to analysis.
In the temperature control, if there is only a series of control operations, such as ramping the temperature up and down, this will be insufficient for efficient information collection. Moreover, because of the limitation in That is, in the feature quantity calculating function that is disclosed in the JP '439, there is a limit to the amount of information that can be stored, and thus it is insufficient. On the other hand, with the data logger disclosed in the JP '603, information that is not required for control operations is included, causing the amount of data that is collected to be too large, complicating the handling thereof, which is inconvenient. Consequently, it is desirable in an effective information collecting function that is specialized for control operations to have an improved function that is not too complex and wherein the information deficiency is not too great. In particular, there is the need for improvements for broader use in specialty situations, rather than just for handling ramping of temperatures up and down.
An alarm function, for example, for when an open circuit is detected in a sensor, is included in a temperature controller, which is a representative example of a simple PID controller. The time band before and after an alarm event is a time band that is subject to analysis of the cause for the alarm, and thus particularly detailed time series data are required. However, there is a problem in that no function for collecting detailed time series data for the time band before and after an alarm event has been achieved in the conventional PID controller.
The present invention was created in order to solve the problem set forth above, and an aspect thereof is to provide a PID controller, and data collecting method, able to collect detailed time series data before and after an alarm event, assuming that it will be incorporated into low-cost production such as with a simple PID controller, such as a temperature controller.